1. Field of Invention
The present invention relates to a group III nitride compound semiconductor device.
The present application is based on Japanese Patent Application No. Hei. 11-65880, which is incorporated herein by reference.
2. Description of the Related Art
It is known that group III nitride compound semiconductors can be utilized, for example, as blue light-emitting devices. As a method of producing a group III nitride compound semiconductor device, there has been heretofore proposed a method comprising the steps of: growing a buffer layer of AlN or GaN on a sapphire substrate; growing a layer of GaN or AlGaN (hereinafter referred to as undercoat layer) by several microns on the buffer layer; and growing a layer of InGaN (hereinafter referred to as InGaN layer) on the undercoat layer (see Japanese Patent No. 2751963).
In the aforementioned method, however, the composition of the InGaN layer was different from the composition of the undercoat layer (AlGaN or GaN). Hence, the former was heteroepitaxially grown on the latter. Moreover, when the two layers were to be formed by means of a metal organic chemical vapor deposition method (hereinafter abbreviated as MOCVD method), the temperature for the growth of the undercoat layer (AlGaN or GaN) was generally about 1000° C. whereas the temperature for the growth of the InGaN layer was from about 700° C. to about 900° C. Improvement in crystallinity of the InGaN layer formed on the undercoat layer was limited because of the problem in heteroepitaxial growth and difference between the growth temperatures as described above.